1. Field of the Invention
The present invention relates to multiple systems sensing for a coexisting radio network, and more particularly to multiple systems sensing for construction of a cognitive radio network or for UWB communications demanding Detect And Avoid (DAA).
2. Description of the Related Art
In wireless communication, due to the limited spectrum resource, the coexistence of variable radio systems over common spectrum is becoming a trend. For example, the UWB communications demanding Detect And Avoid (DAA) and the cognitive radio (CR) are two possible realizations that comply with the coexistence demand.
The concept of cognitive radio is that transmitters and receivers can alter communication parameters based on a variety of factors such as the nature of the communication being transmitted, the availability of licensed or unlicensed frequencies, network state, noise, bandwidth, etc. However, spectrum sensing of cognitive radios conventionally only possesses link level distinguishing ability (i.e. idle and thus available, or used and therefore unavailable). In the complicated case of cognitive radio networks (CRNs) with more cognitive radios incorporated in, spectrum sensing should achieve networking level functions that cognitive radio networks can communicate with either primary systems (maybe more than one primary system) or other cognitive radios (secondary systems) to optimize entire network efficiency over radio spectrum. Therefore, in addition to sensing the idle status of spectrum, identification of multiple systems is critical for establishing connections and building up the cognitive radio networks.
Spectrum sensing techniques traditionally include energy detection, CP existence, pilot detection, spatiotemporal sensing. Sensing under a multiple coexisting environment such as 2.4 GHz ISM band is considered by distributed classification. However, with inter-system interference, traditional techniques are not enough and thus a more reliable and general multiple systems sensing algorithm is needed to overcome this challenge. In the invention, we propose a methodology exploiting the system-specific identification of multiple active systems, over uncorrelated Rayleigh fading channels to identify spectrum utilization status. In addition to energy detection and carrier locking, we identify the fundamental frequencies of candidate communication systems periodically filtered by pulse shaping filters. To accomplish the multiple systems sensing, we have to further exploit the unique power spectrum density pattern of systems. If the additive noise is colored Gaussian with unknown covariance matrix, the power spectrum density pattern methodology might not apply. We may further make use of high-order statistics with cumulants that are blind to any kind of a Gaussian process to ensure the success of our multi-system sensing for cognitive radio networks.